Cellular and humoral parameters of immunological responsiveness may play an important role in conditioning the outcome of severe thermal injury. A better understanding of the alterations in immunological function produced by severe burns may, therefore, produce improvements in current results of therapy. The proposed studies are aimed specifically at: (a) assessment of the ability of agents capable of stimulating the reticuloendothelial system (RES) to increase resistance to thermal injury; (b) evaluation of potential hazards of therapeutic agents normally cleared by the RES, with particular reference to the use of heterologous antilymphocyte (or thymocyte) globulins (ALG) to prolong skin allograft survival in burned subjects; (c) studies of the ability of controlled thermal injury to trigger autoimmune organ-specific tissue damage; (d) more precise definition of the kinetics of generation of antibody-forming cells in burned animals; (e) evaluation of the ability of lymphocytes obtained from burned animals to respond to T-cell and B-cell specific polyclonal activators, and studies of the allogeneic reactivity of burned mouse spleen and thoracic duct lymphocytes in vitro.